From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934058AbXEGNx1 (ORCPT ); Mon, 7 May 2007 09:53:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934053AbXEGNx0 (ORCPT ); Mon, 7 May 2007 09:53:26 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:4734 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934023AbXEGNxY (ORCPT ); Mon, 7 May 2007 09:53:24 -0400 Date: Sat, 5 May 2007 11:42:54 +0000 From: Pavel Machek To: Linus Torvalds Cc: "Rafael J. Wysocki" , Nigel Cunningham , Pekka J Enberg , LKML Subject: Re: Back to the future. Message-ID: <20070505114253.GA5119@ucw.cz> References: <1177567481.5025.211.camel@nigel.suspend2.net> <200704280041.17617.rjw@sisk.pl> <200704280145.26253.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > The "let's stop all kernel threads" is superstition. It's the same kind of > > superstition that made people write "sync" three times before turning off > > the power in the olden times. It's the kind of superstition that comes > > from "we don't do things right, so let's be vewy vewy quiet and _pray_ > > that it works when we are beign quiet". > > Side note: while I think things should probably *work* even with user > processes going full bore while a snapshot it taken, I'll freely admit > that I'll follow that superstition far enough that I think it's probably a > good idea to try to quiesce the system to _some_ degree, and that stopping > user programs is a good idea. Partly because the whole memory shrinking > thing, and partly just because we should do the snapshot with hw IO queues > empty. > > But I don't think it would necessarily be wrong (and in many ways it would > probably be *right*) to do that IO queue stopping at the queue level > rather than at a process level. Why stop processes just becasue you want > to clean out IO queues? They are two totally different things! Actually, I'd like to stop I/O queues; if there was easy way to do that, I'll happily switch. Notice that we'll need to stop 'I/O queues' of the char devices, too... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html